Enzymatic bleach compositions comprising a hydrogen peroxide-generating system are well known in the art. For instance, GB-A-2 101 167 (Unilever) discloses an enzymatic hydrogen peroxide-generating system comprising a C.sub.1 -C.sub.4 alkanol oxidase and a C.sub.1 -C.sub.4 alkanol. Such enzymatic bleach compositions may be used in detergent compositions for fabric washing, in which they may effectively provide a low-temperature enzymatic bleach system. In the wash liquor, the alkanol oxidase enzyme catalyses the reaction between dissolved molecular oxygen and the alkanol to form an aldehyde and hydrogen peroxide.
In order to obtain a significant bleach effect at low wash temperatures, e.g. at 15-55.degree. C., the hydrogen peroxide must be activated by means of a bleach activator. Today, the most commonly used bleach activator is tetra-acetyl ethylene diamine (TAED), which yields peracetic acid upon reacting with the hydrogen peroxide, the peracetic acid being the actual bleaching agent.
WO-A-89/09813 (Novo-Nordisk) discloses enzymatic bleaching compositions comprising a source of hydrogen peroxide and a peroxidase, and WO-A-91/05839 (Novo Nordisk) discloses enzymatic anti dye-transfer compositions comprising an (a) an enzyme exhibiting peroxidase activity and a source of hydrogen peroxide or (b) an enzyme exhibiting oxidase activity on phenolic compounds. The compositions are said to bleach any dissolved dye so that no dye can redeposit upon the fabric.
Peroxidases and laccases are well described in the art as enzymes which can be used to catalyse the oxidation reaction of a substrate with hydrogen peroxide or molecular oxygen, respectively. Other applications of these enzymes in oxidative processes include, amongst others, polymerization of lignin, in-situ depolymerization of lignin in Kraft pulp, bleaching of denim dyed garments, polymerization of phenolic substances in juices and beverages and hair bleaching (WO-A-92/18683, WO-A-95/07988, WO-A-95/01426).
It is known that laccases and (haem) peroxidases generally oxidize their substrates via electron transfer reactions, such as oxidation of hydroquinones to quinones or formation of radicals that may subsequently react further with other available molecules, in which oxygen and hydrogen peroxide act as the electron acceptor, respectively. These reactions may lead to bleaching of the substrate, but on the other hand, they may cause darkening of the substrate due to polymerization. The latter phenomenon is well known from browning reactions between polyphenolic substrates and laccases or polyphenol oxidases in nature.
A completely different way of oxidizing chromophores is by incorporation of one or more oxygen atoms; these reactions are performed by mono- and di-oxygenases using molecular oxygen. Many dioxygenases, such as the catechol dioxygenases and protocatechuate dioxygenase, have been described in the literature. In general, these enzymes are part of complex intracellular multi enzyme systems which may be bound to membranes.
EP-A-086 139 (Transgene) relates to the cloning and expression of the xylE gene from Pseudomonas putida, coding for such an intracellular dioxygenase called 2,3-catechol oxygenase by means of recombinant DNA techniques. The thus produced (intracellular) 2,3-catechol oxygenase may be applied in the food industry and in the cosmetic/pharmaceutic industry and, inter alia, the application of such dioxygenases for disinfecting surfaces is mentioned.
Although several enzymatic bleach systems have been proposed, there is still a need for alternative or improved enzymatic bleach systems. In particular, the enzymatic bleach system should be capable of bleaching broad spectrum of stains, using dissolved molecular oxygen from the air.
It is therefore an object of the present invention to provide alternative or improved enzymatic bleach systems which, in particular, should be capable of bleaching broad spectrum of stains, using dissolved molecular oxygen from the air. It is a further object of the present invention to provide an alternative or improved enzymatic bleach process.
We have now surprisingly found that enzymes from extracellular origin, capable of oxidizing substrates by the build-in of one or more oxygen atoms into the substrate using molecular oxygen, can effectively be used for the bleaching of chromophores present in stains on textile. Moreover, we have found that oxygenases secreted by microorganisms in the fermentation fluid are much more effective than the catechol dioxygenase described in the art. This appears to be due to a much broader substrate specificity and the ability to oxidize complex chromophores, in contrast to the described catechol dioxygenase which only works on simple substituted phenols.
Accordingly, the above and further objects of the invention are achieved by the enzymatic bleach composition of the invention which is characterized in that it comprises one or more surfactants and an enzyme of extracellular origin, capable of oxidizing substrates by the build-in of one or more oxygen atoms into the substrate using molecular oxygen.